I think it is worth noting that the combined Rock Band and Guitar Hero sales are around GH3's sales last year. I don't think the music market has shrunk, per se--although the economy has definitely taken a huge shit on expensive peripheral-based games--I just think the base is currently split between the two franchises. If WoW weren't recession-proof, Activision would probably be disappointed, of course.
Other numbers: Wii Music did better than it deserved but worse than it should have given the hardware sales. The shitty economy just reinforces the trend that was already there, for probably the rest of this generation Americans are going to be buying PS2s, Wiis, DSes, and PSPs. People will increasingly buy their games used, play free games online, or just pirate them. The PS3 is priced so far out of the market right now that I honestly expected it to do worse. Post-holiday numbers this year are going to be anemic, maybe even returning to the early 2007 ridiculousness. The 360's price drop seems to be paying off, though I haven't been keeping up with things so I have no idea whether Microsoft is actually making a profit on this venture.